A transport layer protocol has several responsibilities, One is to create a process-to-process (program-to-program) communication; TCP uses port （1） to accomplish this. Anotherresponsibility of a transport layer protocol is to create a（2）and error-control mechanism atthe transport level. TCP uses a sliding（3）protocol to achieve flow control. It uses theacknowledgment packet, time-out, and retransmission to achieve （4） control. The transportlayer is also responsible for providing a connection mechanism for the application program. Theapplication program sends （5）of data to the transport layer. It is the responsibility of thetransport layer at the sending station to make a connection with the receiver.

（2）是（）

A.procedure

B.function

C.route

D.flow

在价值工程活动中的方案创造阶段，要求专家们根据有关研究对象的问题和要求，在互不商量的情况下提出各种建议和设想的方法是（）。

A．头脑风暴法

B．哥顿法

C．德尔菲法

D．专家检查法